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Question

How to reach IFC features "properties" (various property sets) and attach them as attribute to the correct feature for GIS output

  • 27 January 2021
  • 1 reply
  • 65 views
J

Hello !

I am struggling with IFC files and the extraction of their various propery sets.

My goal is

-to extract relevant properties for features in a IFC files (property sets depends on the object type in the IFC file and for each object type, there can be multiple property sets),

- to attach them to the right features as attribute for a GIS output (not CityGML though, so BIM tutorial to create CityGML are not entirely helpful, I need, unfortunately, a more "basic" format : feature+attributes in one layer).

 

I have looked in the forum and watch some webinars but somehow I am still not clear on how to proceed. I read that the revit reader could help but in my case, many many properties are simply not read, which is understandable since each IFC can be organized in its own way, with as many relations and property sets as one might want.

So I need to do this "manually", i.e. create adapted workflows depending on the IFC files. And I do not know how to proceed. So if you can help me by describing the procedure and the tranformers/settings to use, it would be great.

Attached is an example of a features with multiple property sets.

Thanks a lot in advance for any help !

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1 reply

daveatsafe
Rank
Userlevel 2
Badge +17

Hi @jacquinod​ ,

The IFC data has a pretty complex structure, where the property set info is stored in the feature's geometry hierarchy, rather than as attributes on the feature header. The technique I usually use to simplify it is:

  • Use a GeometryPropertyExtractor transformer to promote the property sets to attributes
    • Change Prefix Extracted Trait With Geometry Name to 'Yes'
    • Leave all other settings as defaults
  • Add a GeometryPartExtractor to extract the 3D 'Body' geometry and discard the rest
    • Click on the Geometry XQuery button
    • set This part - Geometry Name = Body as first test clause
    • set The parent of this part - Hierarchy Position - Is - Root Node as second clause
    • set Pass Criteria to AND

The promoted attribute will not be automatically exposed to the workbench, although they will be present on the feature. To expose the new attributes:

  • Pick Run from the Workbench menu - click Enable Feature Caching
  • Run the workspace
  • Add an AttributeExposer between the GeometryPropertyExtractor and the GeometryPartExtractor
  • Edit the Properties of the AttributeExposer and choose Import - From Feature Cache
  • Select all attributes, then click the Import button

Now the data will be ready to export to GIS as 3D features.

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